Say you have a plain text:
How are you today?
and you encrypt it so it becomes:
Now you have multiple people that need to know the plain text of this cipher text but you do not want them to have the same key. It might be they each come up with their own password or they all have a key which identifies that individual.
Now one way of doing this would be adapting this answer so every user encrypts the one key with their own key so you'd get ten encrypted files (for ten people) of the same key. (I don't know if this is good practice but I think it's a secure option.)
Are there any other ways of having different people using different keys to get the same plain text from the same cipher text (and vice versa)? Is there a special algorithm for this?